(1) Field of the Invention
This invention relates to a fibrous bundle in which fibrous elements differing in characteristic features are mingled substantially uniformly. More particularly, the invention relates to a fibrous bundle composed of fibrous elements, at least some of them having a thickness varying along the lengthwise direction thereof, in which changes of characteristic features are due to variation of the thickness, and also relates to a method and apparatus for the production of such fibrous bundle.
By the term "fibrous bundle" used in the instant specification and appended claims are meant fibrous bundles of a great number of fibrous elements, such as a bundle of filaments, e.g., a multifilament yarn or tow, a bundle of staple fibers, e.g., a sliver, roving or spun yarn, and a bundle of filaments wherein parts or all of the bundle-constituting filaments involve broken points.
In this invention, fibrous elements of the fibrous bundle are elements of man-made fibers, which have been prepared from man-made fiber filaments.
(2) Description of the Prior Art
In general, a bundle of filaments is prepared from man-made fibers by spinning and drawing, and in ordinary filament bundles, all of bundle-constituting filaments are substantially uniform in the thickness and various characteristic features.
Also, fibrous bundles composed of filaments differing in characteristic features have been developed and proposed. These fibrous bundles are different from uniform filament bundles in various aspects.
These fibrous bundles, comprising in the mingled state fibrous elements differing in characteristic features, are roughly divided in two types. In one type, a plurality of groups of fibrous elements are mingled, and in respective groups, each of fibrous elements per se is provided with uniform characteristic features, although the characteristic features of fibrous elements of one group are different from those of fibrous elements of another group. In the other type, each of elements is provided with portions differing in characteristic features distributed in the lengthwise direction thereof.
The main difference between these two types of fibrous bundles is most conspicuous when fibrous elements differing in the stress-strain characteristics are mingled. When these fibrous bundles are drawn, in the former type fibrous elements having a low elongation are first broken and in the broken fibrous elements the positions of breakages thereof do not substantially differ in the fibrous bundle; whereas in the latter type, breakage is caused in portions of poor strength and the positions of breakage thereof are not uniform in the fibrous bundle. When it is intended to prepare a filament bundle resembling spun yarn by creating fluffs on a fibrous bundle, a fibrous bundle of the latter type is preferably employed.
Another difference is conspicuous when fibrous elements differing in the color effect or dyeability are mingled. In a fibrous bundle of the former type, fibrous elements of one group tend to gather with respect to the cross-section of the bundle so that uniform mingling of groups of fibrous elements in a cross-section of the bundle can not be attained. If uniform mingling is attained, fibrous elements of each group tend to gather during the processing. In the case where mingling of groups of fibrous elements with respect to the cross-section is not uniform, even if the thickness variation of the fibrous bundle along the lengthwise direction is substantially uniform, extreme unevenness of the color effects is manifested in a knitted or woven fabric formed from such fibrous bundle. In contrast, in the case of a fibrous bundle of the latter type, if the variation of the characteristic features of each fibrous elements are uniformly distributed with respect to the lengthwise direction thereof, uniform mingling with respect to the cross-section of the bundle can be created. However, it is very difficult to create such distribution of the characteristic features of fibrous elements that they are distributed uniformly in the lengthwise direction of the bundle.
In the case of mingling of fibrous elements differing in characteristic features other than the color effect or dyeability, a difference similar to that pointed out above with respect to mingling of fibrous elements differing in color effect or dyeability is observed between the two types of fibrous bundles. However, such difference is not so conspicous as in the case of mingling of fibrous elements differing in color effect or dyeability.
The present invention is related to a fibrous bundle of the above-mentioned latter type, in which differences of characteristic features are due to variations of thickness in each fibrous element.
Various fibrous bundles of the latter type are known. As methods for producing these fibrous bundles, there are known, for example:
a method in which such factors as the draw ratio, the distance of the passage of the fibrous bundle the atmosphere of the passage of the fibrous bundle and resistance to the running fibrous bundle, etc, are changed at the spinning or drawing process; PA1 a method in which drawing is carried out at a draw ratio corresponding to a rate of elongation of the fibrous bundle in a constant tension elongation region; PA1 a method in which at the heat-drawing process, a fibrous bundle is drawn and heated for such a short time that respective fibrous dements are not uniformly heated, and; PA1 a method in which, before the drawing step, fibrous elements are scratched or deformed by a heat treatment, a coating treatment with a cracking agent or a treatment for forming slacks or rings in the fibous elements is performed, and then, the drawing operation is carried out. PA1 wherein d.sub.1 stands for the diameter (mm) of the frictional resistance-imparting member having a pin-like shape, d.sub.2 stands for the diameter (mm) of the drawing roller, and d.sub.3 stands for the distance (mm) between the drawing roller and the frictional resistance-imparting member.
In most fibrous bundles prepared according to the above-mentioned known methods, the distribution phase of the thick portions of respective fibrous elements are created uniformly along the lengthwise direction thereof in the case of cold drawing, and in case of heat drawing, portions having an intermediate thickness are formed in the respective fibrous elements so that the intended effects due to variations of the thickness are diminished. Further, in the case of cold drawing, from a technical point of view in the known art, it is clear that the number of thick portions (or thin portions) in the fibrous elements is increased, but the distribution state is not good and mingling of thin and thick portions is very uneven with respect to the lengthwise direction of the fibrous bundle. In the case of heat drawing, the distribution state is improved over the case of cold drawing, but the number of thick portions (or thin portions) cannot be increased and mingling of thick and thin portions is very uneven with respect to the lengthwise direction of the fibrous bundle.